Approximately 3.5 kb of the 5'-upstream region of the Drosophila NK-2 homeobox gene was sequenced and putative binding sites were found for proteins that regulate gene expression. The first expression of the NK-2 gene coincides in time and place with the appearance of the neurogenic anlage, which suggests that NK-2 homeobox protein functions as an activator of the gene program that leads to the formation of part of the brain, subesophageal ganglion, and ventral nerve cord. Expression of the NK-1 homeobox gene is initiated 6 hr after fertilization in ganglion mother cells that give rise to a subset of neurons in the CNS and in a subset of founder muscle cell. Many transgenic Drosophila lines were generated by transposition of a P element that contains a beta- galactosidase gene that express beta-galactosidase during embryonic development only in the nervous system. Two novel mouse homeobox cDNAs were cloned (Hox 1.11 and CL-125). Hox 1.11 cDNA encodes a protein with a homeodomain similar to that of Hox 2.8 and an acidic domain. The Hox 1.11 gene was mapped to mouse chromosome 6. CL-125 cDNA encodes a protein with a homeodomain related to that of Hox 1.6. Two novel species of mouse Pou-box-homeobox DNA were cloned (C-1 and G-1). The C-1 gene is expressed only in adult brain and salivary glands. Neuroblastoma or hybrid cell lines were found that express brain-specific species of C-1 mRNA. Mouse genomic DNA fragments that activate replication of an E. coli-mammalian cell shuttle vector were selectively amplified and cloned. Some of the DNA clones contain novel enhancer or promoter sequences. The 5'-upstream region of a novel voltage-sensitive calcium channel alpha1- subunit gene from rat brain was cloned and sequenced. Expression of this calcium channel gene in NG108-15 cells was dependent upon elevation of cellular cAMP for several days. Fragments of DNA from the 5' upstream region of the calcium channel gene activate transcription of a reporter gene. The cAMP-dependent regulation of calcium channel mRNA ultimately regulates the efficiency of transynaptic communication.